1. Field of the Invention
The present invention relates to a scroll controller capable of converting data into an image which can be visually displayed and visually displaying the image, which scroll controller may be suitably embodied in personal computers and small electronic apparatuses.
2. Description of the Related Art
Hitherto, as a so-called scroll control in a small electronic apparatus, there has been a technology of conducting a scroll operation by setting a moving direction and a moving quantity by points as described in Japanese Unexamined Patent Publication JP-A 9-69037 (1997) for example.
FIGS. 13A and 13B are a diagrammatic view and a graph for explaining the related art scroll operation. An outer frame 83 in FIG. 13A denotes an edge of a scroll area of a display screen of a display device, i.e., a visual display area where an image scroll operation is carried out.
A reference point 85 is set at the center of the scroll area. A specified point 130 is a point within the scroll area corresponding to a point which has been inputted and specified by an user of the electronic apparatus through a coordinate input device.
When the specified point 130 is specified, a central processing unit scrolls a part of data image displayed on the display screen of the display device so that an image displayed at the position of the specified point 130 is displayed at the position of the reference point 85 via six relay points 131.
That is, the image which has been displayed right under the point where the user has pressed the coordinate input device 13 is scrolled so as to be positioned at the center of the display device 12 step by step. The scroll is performed so as to switch images for example in this prior art example.
A moving quantity of one step in scrolling the image is specified to be equal to a distance obtained by dividing the distance between the reference point 85 and the specified point 130 into seven equal parts for example. The image is switched and scrolled by 1/7 of the distance between the reference point 85 and the specified point 130 in the first step and then it is scrolled to the position of 2/7 of the distance between the reference point 85 and the specified point 130 in the second step. The image which has been displayed at the position of the specified point 130 is displayed at the position of the reference point 85 by repeating the above-mentioned procedure by seven times. Accordingly, the greater the distance between the reference point 85 and the specified point 130, the greater the distance of one step where the image is scrolled becomes.
The image is scrolled in the direction from the specified point 130 to the reference point 85 in the scroll operation of this prior art example. That is, when the point 130 is specified, the image is scrolled in the direction indicated by a vector 132, i.e., in the upper left direction, in this prior art example.
FIG. 13B is a graph showing the relationship between a time and a speed in scrolling the image of this case. Assuming a time required for scrolling from the specified point 130 to the relay point 131a is t10 and the speed from the specified point 130 to the relay point 131a is s10, the moving distance of one step may be represented as "t10.times.s10".
The moving distance between the respective remaining points may be represented as "t10.times.s10" in the same manner and the moving speed in each unit time from the specified point 130 to the reference point 85 is constant. Thus, the electronic apparatus 11 of this prior art example can scroll the image stepwise in any direction.
However, the above-mentioned prior art technology has had a problem that because the scroll speed is all the same, it confuses the user because the image moves quickly to the specified position and the moving directionality cannot be get when a display device such as a liquid crystal display whose display processing speed is low is used.
Further, the related art technology has another problem that it becomes difficult to confirm a scroll quantity as the scroll speed increases and that the scroll had to be released in order to confirm the scroll quantity.